Conductive cellulose nanocrystals, method of producing same and uses thereof

ABSTRACT

The present disclosure provides a core-shell nanocomposite material comprising an intrinsically conductive polymer (ICP) and surface-modified cellulose nanocrystals (CNCs) as well as synthesis for preparing same and its use thereof in various applications.

FIELD OF THE DISCLOSURE

The present disclosure provides a core-shell nanocomposite materialcomprising an intrinsically conductive polymer (ICP) andsurface-modified cellulose nanocrystals (CNCs) as well as synthesis forpreparing same and its use thereof in various applications.

BACKGROUND OF THE DISCLOSURE

The demand for various consumer electronics and hybrid vehicles capableof delivering a high power supply in short pulses with an extremely longcycle life has prompted extensive interest in supercapacitors (SPs).

Intrinsically conductive polymers (ICP) have demonstrated theirusefulness in a wide variety of applications, such as sensors,anti-static/electromagnetic interference shielding, organiclight-emitting diode (OLED), supercapacitors, etc. due to their superiorphysical and chemical properties (Lange, U.; Roznyatovskaya, N. V.;Mirsky, V M., Analytica chimica acta 2008, 614 (1), 1-26; Li, C.; Bai,Shi, G., Chemical Society reviews 2009, 38 (8), 2397-409) . However, theinherent problems with ICPs such as low solubility, intractable phase,poor mechanical properties make them difficult to process into usefulproducts (Schultze, S. W.; Karabulut, H., Electrochimica Acta 2005, 50(7-8), 1739-1745).

One example of a typical ICP is polypyrrole (PPy) that has beenintensively studied for decades as a promising electrode material forSPs due to its ease of synthesis, low cost, good conductivity, stabilityand excellent specific capacitance (Cs). However, being mechanicallyweak, PPy experiences significant structural breakdown resulting fromvolumetric swelling/shrinkage resulting in a fast capacitance decay overextended cycles (less than 50% retention of the initial capacitanceafter 1000 cycles). Another drawback is the poor processibility andunsatisfactory specific capacitance (Cs) (F/g) due to agglomerationresulting from strong intermolecular, intramolecular interactions andpossible cross-linking of PPy chains.

Cellulose Nanocrystals (CNCs) extracted from wood fibers by acidhydrolysis are rod-like crystals. The attractive features are: (i) it isstronger than steel yet incredibly light, (ii) high aspect ratio andspecific surface area, (iii) enriched surface active groups, (iv)biodegradability, (v) abundance etc. This makes CNC a promisingstructural nanomaterial (as reinforcing agents), or functionalnanomaterials for the fabrication of other functional nanocomposites.

The Applicant has previously described in PCT/CA2014/050570 an in situchemical polymerization, for preparing an ICP/CNC system with acore-shell structure that possessed attractive supercapacitor behavior.

The precise control of a uniform and thin ICP-coated (such asPPy-coated) nanocomposites at nanoscale remains a challenge since it isdifficult to fully prevent the formation of free polymer particles inbulk solution, and deposited conjugated polymers on the nanoparticlesare often irregular and thick. For example, PPy-based hybrid materialsloose their fine fibril structure due to agglomerations.

SUMMARY OF THE DISCLOSURE

In one aspect, there is provided a composite having a core-shellarrangement, said composite comprising cellulose nanocrystal (CNC) asthe core, a first layer comprising at least one surface agent in contactwith said CNC and a second layer comprising at least one intrinsicallyconductive polymer (ICP) in contact with said surface agent

In a further aspect, there is provided a process for preparing thecomposite having a core-shell arrangement as defined herein, saidprocess comprising the steps of:

-   dispersing the cellulose nanocrystal (CNC) in a solution;-   mixing the CNC solution and at least one surface agent to cause    adsorption of said surface agent on the CNC surface and form said    first layer;-   adding at least one monomer of said intrinsically conductive polymer    and polymerizing said monomer to form said second layer in contact    with said first layer comprising the surface agent; and-   isolating said composite.

A core-shell conductive polymer/cellulose nanocrystal composite preparedby the method as defined herein.

A composite material comprising the composite having a core-shellarrangement as defined herein.

A process for preparing a supercapacitor electrode comprising casting aslurry of the composite having a core-shell arrangement as definedherein on an electrode followed by drying of said slurry.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, with reference to the drawings, inwhich:

FIG. 1 is a schematic representation of the experimental strategy toprepare the core-shell structure in accordance with one embodiment ofthis disclosure;

FIG. 2(a)-(h) are TEM images of polypyrrole polymerized onpoly(N-vinylpyrrolidone) coated CNC (PPy/PVP/CNC) nanorods in accordancewith the disclosure;

FIG. 3 is TGA curves for certain PPy/PVP/CNC nanorods in accordance withthe disclosure;

FIG. 4 is a UV-Vis spectra of PVP adsorbed CNC, PPy coated CNC andcertain PPy/PVP/CNC nanorods in accordance with the disclosure;

FIG. 5 is a FT-IR spectra for CNC, PVP, PPy coated CNC and certainPPy/PVP/CNC nanorods in accordance with the disclosure;

FIG. 6 is a graph illustrating the effect of CNC surface modification onthe zeta-potential and conductivity of the hybrid material ofPPy/PVP/CNC nanorods in accordance with the disclosure;

FIG. 7 illustrates the effect of polymerization time on the conductivityand zeta-potential of a PPy/PVP/CNC nanorod in accordance with thedisclosure;

FIG. 8 represents the specific capacitance from cyclic voltammetry testfor a PPy/PVP/CNC nanorod in accordance with the disclosure polymerizedat different time intervals; and

FIG. 9 is illustrating the Capacitance loss between nanorods inaccordance with the disclosure and PPy coated CNC prepared by analternative process.

DETAILED DESCRIPTION OF THE DISCLOSURE

Additional details describing various embodiments of the presentsurface-modified cellulose nanocrystals (CNCs), comprising a surfaceagent, and an intrinsically conductive polymer is provided.

As used herein, the term “intrinsically conductive polymer” refers toorganic polymer that conducts electricity. In one embodiment, theconductive polymer of said conductive polymer/cellulose nanocrystalcomposite is polypyrrole, polyaniline, polyindole, polythiophene,poly(3-methylthiophene, poly(N-methyl aniline), or poly(o-toluidine).Preferably, the conductive polymer is polypyrrole.

The CNCs herein are rod-like crystals with a mean diameter of 10-20 nmand lengths of 200-400 nm. It can practically be extracted from varioussources like cotton, wood, alga etc. In this case, we usedkraft-bleached pulp, which was obtained from Domtar and the CNC wasproduced by Celluforce Inc. (Montreal, Quebec Canada).

As described herein, the CNCs are coated with a surface agent before itis further coated with the ICP by polymerization of the correspondingmonomer.

The composite having a core-shell arrangement, as described herein canbe viewed as conductive nanocomposite rods (or rod-like) havingdimensions as shown in the TEM images.

A method is described for synthesizing electrically conductive CNCs bycoating them with a surface agent which is PVP and an ICP which is PPy.Usage of CNC as the substrate is believed to facilitate the linearly,well-ordered growth of conductive polymers due to the ‘templatingeffect’ (Xinyu Zhang, V. J. G, and Sanjeev K. Manohar, Journal of theAmerican Chemical Society 2004, 126 (14), 4502-4503). It also resolvesthe intrinsic problem of poor mechanical strength and poorprocessability associated with these polymers.

As described herein, the present disclosure provides a controlledsynthesis of individually coated cellulose nanocrystals (CNCs) as thecore, a first layer of at least one surface agent in contact with saidCNC and a second layer of at least one intrinsically conductive polymerin contact with said surface agent . The degree of surface modificationof CNC can be controlled as described herein and allows to achieve thedesired PVP coating and PPy polymerization. The examples hereindemonstrate the synthetic steps and comprise a treatment of CNC with asurface agent and adding the ICP corresponding monomers in the mixtureto allow polymerization

There is therefore provided a process for preparing the composite havinga core-shell arrangement as defined herein, said process comprising thesteps of:

-   dispersing the cellulose nanocrystal (CNC) in a solution;-   adding to the CNC, a solution of at least one surface agent,    optionally in solution, to cause adsorption of said surface agent on    the CNC surface and form said first layer (i.e. for PVP/CNC);-   adding a polymerization catalyst, optionally in solution, to the    PVP/CNC solution;-   adding at least one monomer, optionally in solution, of said    intrinsically conductive polymer and polymerizing said monomer to    form said second layer in contact with said surface agent; and-   quenching said polymerization and isolating said composite.

In one embodiment, surface agents that can be used in this disclosureinclude without limitation Poly(4-vinylpyridine) (P4VP),poly(N,N-dimethyl acrylamide) (PDMA), poly(N,N-dimethyl acrylamide)(GTMAC), Polyethylenimine(PEI), etc. Although other amphiphilic agentscan be used, MP is a most commonly used and cost effective surfaceagent.

By using a common surface agents, preferably PVP, it is believed thatthe agent will wrap around CNC to form the hydrophobic layer and promotethe stronger interaction between CNC and the pyrrole monomers. It alsoact as a stabilizer due to steric hindrance to enhance the colloidalstability of the hybrid material and prevent further aggregation. It isalso believed that the amphiphilic properties of PVP provide activesites on the CNC to induce the polycationic PPy growing towardshomogeneous coating.

Herein, the mass ratio of PVP to CNC can be varied to achieve desirablecolloidal stability and conductivity. In one embodiment, the surfaceagent can be mixed with the CNC at different surface agent/CNC massratio. For example, the surface agent/CNC can range from 5/100 to100/100. Other embodiments include about 20/100, 40/100 or preferablyabout 10/100. In one embodiment, when the surface agent is PVP, said PVPand CNC can be mixed for about 24 hours to ensure appropriate adsorptionof PVP on the CNC surface.

In one embodiment of the method, the monomer corresponding to the ICP,such as a pyrrole monomer, and said surface agent/CNC are mixed for asuitable time interval and controlled temperature, preferably for a timeduration of about one hour. Preferably the temperature is from about 0to 5 degrees.

In one embodiment of the method, said step of polymerization of saidmonomer is carried for a controlled time and temperature, preferably forabout 16 hours, preferably at a temperature of from about 0 to 5degrees.

Polypyrrole (Ppy) can be synthesized via the oxidation of pyrrole withan oxidant. The most commonly used oxidizing agents are oxidativetransition metal ions. Although FeCl₃ is commonly used, other salt suchas Fe(NO₃)₃, Fe(ClO₄)₃, Fe₂(SO₄)₃, K₃Fe(CN)₆, FeBr₃, CuCl₂ and CuBr₂ canbe used. In one embodiment of the method, said oxidant is ferricchloride. Preferably, said ferric chloride is dissolved in water and isadded dropwise to the reaction mixture. In the case of ferric chloride,it is believed that cationic ferric ions has better affinity to attachon the surface of negatively charged CNCs and induce the polymerizationto occur in situ.

In one embodiment of the method, said monomer, such as a pyrrolemonomer, and said cellulose nanocrystals are mixed in neutral solution.Preferably, said pyrrole monomer is dissolved in water and is addeddropwise to the reaction mixture.

In one embodiment of the method, said step of polymerization of saidmonomer is carried for a controlled time and temperature, preferably forabout 16 hours, preferably at a temperature of from about 0 degrees.

In one embodiment of the method, said step of said conductivepolymer/cellulose nanocrystal comprised of quenching the saidpolymerization. For example the reaction mixture can be treated toremove excess oligomers and unreacted chemicals, for example byultrafiltration. In a typical ultrafiltration approach, the filtrationis applied several times until the filtrate became colorless andtransparent.

In one embodiment, the isolated PPy/PVP/CNC can be further processedincluding drying steps (e.g. freeze-dried) and the dried fine powderpressed or the slurry can be casted (e.g. on an electrode).

In specific embodiments described herein, the surface-modified CNCcoated with PVP and PPy are referred to as PPy/PVP/CNC. In practice,surface modification on CNC to provide the core/shell composite, wasdemonstrated with PVP and PPy, and was achieved through the physicaladsorption of the surface agent (such as PVP) which is believed tomodify the hydrophilic nature of CNC for the favorable growth of the ICP(such as PPy). It is also believed that PVP acts as a steric stabilizerto prevent PPy-coated hybrid particles from further agglomeration.

As used herein, polypyrrole (PPy) modified CNCs as described inPCT/CA2014/050570 are referred to as PPy/TempoCNC.

As described herein, the present disclosure provides a controlledsynthesis of individually coated cellulose nanocrystals (CNCs) as thecore and an intrinsic conductive polymer (ICP) as the shell withimproved coating morphology and enhanced electrochemical properties. Theexamples herein demonstrate the synthetic steps required to prepareembodiments of the disclosure.

The conductive nanocomposites described herein or prepared in accordancewith the method described herein may find uses in a wide range ofapplications including conductive ink, printing electronics, andsupercapacitor material, etc.

Fabrication of PPy/PVP/CNC

The modified CNCs were first prepared by mixing 0.2 wt % CNC solutionwith poly(N-vinylpyrrolidone) (PVP) (MW 10,000 Da) at different PVP/CNCmass ratio of 100/100, 40/100, 10/100, 5/100, and 0/100 (samples denotedas PVP100/CNC, PVP 40/CNC, PVP10/CNC, PVPS/CNC and PVP0/CNCrespectively).

The mixture was mixed for 24 hours to ensure sufficient adsorption ofPVP on CNC surface, which refer herein as PVP/CNC. In one typicalpolymerization for PPy/PVP/CNC, 15 ml of PVP/CNC solution wastransferred to a double-jacketed reaction vessel kept in an ice waterbath at 0° C. Then 364.5 mg of Ferric(III) chloride (FeCl₃) dissolved in5 ml water was added dropwise to the suspension and vigorously stirred.After an hour, 106.5 μl of pyrrole monomer (Py) dissolved in 5 ml waterwas added slowly and the polymerization was left to mix under mildstirring for 16 hours, and the reaction was quenched by repeated washingwith deionized (DI) water in an ultrafiltration cell. Finally, theprecipitates were freeze-dried, and the dried fine powder and waspressed into pellet under 15000 pounds for conductivity measurements.

Assessment of Surface Modification with PVP and PPy by TEM

The degree of CNC surface modification with PVP and its effect on PPygrowth were characterized with a TEM and shown in FIG. 2 in which (a) ispristine CNC; (b) is PVP/CNC (PVP to CNC mass ratio 40%); (c) isPPy/PVP100/CNC; (d) is PPy/PVP40/CNC; (e) is PPy/PVP10/CNC; (f) isPPy/PVPS/CNC; and (g) is PPy/PVP0/CNC. A noticeable size expansion wasobserved (see FIG. 2(a)-(g)) for the PPy/CNCs synthesized at differentPVP/CNC ratio confirming the successful polymerization of PPy shell. Thefibril shape of CNCs with 150-250 nm in length was preserved after PPycoating. The most attractive feature of the PPy coating using thisprotocol is the continuous and uniform PPy coating.

An appreciable increase in the polymerization kinetics from PVP100/CNCto PVP0/CNC was observed based on the accelerating color change fromlight yellow to black, which was confirmed using a TEM. In FIG. 2(c),CNCs were not completely covered by PPy and the magnified image clearlyshowed some exposed CNC surface that was not coated with PPy. Bydecreasing the PVP/CNC mass ratio to 10, a more uniform PPy coating witha thicker shell was formed on the CNC. When the PVP/CNC ratio wasdecreased, the PPy coating became inhomogeneous. When no PVP was added,the PPy coatings were irregular and rougher caused by the fastpolymerization rate (FIG. 2(g).

Thermal Gravimetric Analyses (TGA)

Thermal gravimetric analyses (TGA) were conducted to qualitativelyestimate the mass loading of PPy coating with different degree of CNCmodification with PVP. CNC, PPy, PPy/PVP100/CNC, PPy/PVP10/CNC andPPy/PVP0/CNC were placed in an inert ceramic crucible and heated from 25to 800° C. at a heating rate of 10° C./min in 20 mL/min in airatmosphere.

Due to the higher thermal stability of PPy shell, the higher PPy loadingshould demonstrate milder decomposition closer to the bulk PPy samplesynthesized under the same condition only in the absence of CNCnanoparticles or PVP. Compared with PVP/CNC ratio 100 and 10, the higherPVP addition resulting in the lower PPy loading (35% mass retention forPPy/PVP100/CNC versus 48% PPy/PVP10/CNC at 400 degrees). When no PVP isadded to modify CNC, the PPy loading is comparably low as PPy/PVP100/CNCsample demonstrating incomplete PPy coating or a low PPy polymerizationefficiency. TGA studies for PPy/PVP100/CNC and PPy/PVP10/CNC suggested ahigher thermal stability for the latter. (FIG. 3).

Polymerization of PPy on a Mixture of PVP-Modified and Unmodified CNC

When pyrrole polymerization was performed in a mixture of both modifiedand unmodified CNCs, two diverse end-products were obtained,demonstrating the role of PVP coating on CNC in controlling the growthof PPy. To highlight the role of PVP in the synthesis process, equalmass of pristine CNC with PVP modified CNC were mixed, and allowed topolymerize in the same reaction vessel. The TEM image (FIG. 2(h))revealed two different phenomena: polypyrrole was exclusively grown onPVP coated CNC, while those without PVP displayed inhomogeneously coatedand globular PPy particles deposited on CNC surface.

The PVP is believed to serve two functions: (i) firstly, being anamphiphilic polymer, PVP provides hydrophobic domain that promotes afavorable growth of PPy on CNC surface; (ii) secondly, being amacromolecule, it acts as steric stabilizers that minimizes theagglomeration of PPy/CNC particles producing stable PPy/PVP/CNC hybridnanoparticles in aqueous solution. In addition, hydrogen bonding betweenthe carbonyl groups of PVP and the N-H group of Py promotes a uniformgrowth of PPy on PVP-coated CNC.

UV-Vis Spectra of PPy/PVP/CNC Samples

The UV-Vis spectra of PVP adsorbed CNC shows the characterization peakof PVP at 220 nm indicating the successful attachment of PVP to CNCsample prior to the synthesis. The PPy coated samples at different CNCmodification extent all show a peak at 420 and a broader peak around 900nm, attributing to the characterization peaks of polypyrrole. Due to thecoating of PPy, the buried PVP peak has shifted to a lower wavenumberfrom the incomplete peak shown for sample PPy/PVP100/CNC. (see FIG. 4).

FT-IR Spectra of PPy/PVP/CNC Samples

The PPy coating on CNC was also verified by FT-IR spectroscopy. Thecharacterization peaks indicating the presence of PPy, PVP, and CNC aresummarized in Table 1 below. The most important phenomenon is thatseveral strong peaks in PVP or CNC is significantly suppressed after thePPy coating: e.g. C—H stretching peak for PVP at 2956 cm-1 and C—Ostretching of CNC at 2900 cm-1, which indicates that the two materialsare well embedded in the PPy shell. (see FIG. 5).

TABLE 1 PVP-related 1660 cm⁻¹ C═O stretching 2956 cm⁻¹ C—H(CH₂)stretching 3400 cm⁻¹ O—H stretching vibrations of adsorbed water at thesurface of particles PPy-related 1547 cm⁻¹ C═C stretching of pyrrolering 1455 cm⁻¹ C—N stretching 1152, ═C—H in plane vibration 1302 cm⁻¹CNC-related 2900 cm⁻¹ C—O stretching 3390 cm⁻¹ O—H stretching

Effect of the Degree of CNC Surface Modification on the Zeta-Potential

The conductivity of PPy/PVP/CNC samples prepared at different PVP/CNCratio were evaluated and summarized together with the zeta potential(ZP) in FIG. 6 (top curve: conductivity: lower curve: zeta potential).Due to the negatively charged sulfuric acid groups on the surface (i.e.OSO₃ ⁻), CNC possessed a negative ZP of −55 mV and is extremely stablein aqueous solution. Coating of PPy neutralized the surface negativecharges on CNC by the positively charged PPy backbone. FromPPy/CNC10/CNC, the ZP increased sharply to a positive value signifying ahomogeneous coating of PPy on CNC (i.e. CNCs are fully covered with PPylayers, thereby shielding the sulfuric acid groups). This correlateswith the conductivity data, where PPy/PVP10/CNC possessed the highestconductivity and the most positive ZP. However, when PVP addition wasinsufficient (less than PVP 5%), the ZP decreased to a negative value,indicating a non-uniform PPy coating on the CNC. The conclusions basedon ZP measurements agreed with the TEM observations for all the samplesprepared at different PVP/CNC as shown in FIG. 2 (c)-(g).

Kinetic study: the effect of polymerization time on the conductivity andzeta-potential

The reaction kinetics of the PPy/PVP10/CNC sample were examined bymonitoring the changes in ZP over a period of 24 hours, and FIG. 7summarizes the conductivity and zeta potential as a function of time.The ZP results suggested that the polymerization occurred rapidly in thefirst 3 hours, and it plateau after 10 hrs. The PPy growth on thesurface of CNC approached the conducting percolation threshold at 3hours with the conductivity reaching a plateau and remained constant forthe next 10 hrs and it decreased rapidly after 16 hours. This is notunexpected since extended polymerization often leads to overoxidationthat disrupts the ordered conjugation structure in conductive polymersystems. From observation of the TEM image of the PPy/PVP10/CNC sampleat 24 hours polymerization , the surface morphology of PPy layer wasmuch rougher and fluffier than the sample at 16 hours.

Cyclic Voltammetry and Study of Capacitance

Cyclic Voltammetry (CV) was conducted on different PPy/PVP/CNC systemsusing a three-electrode half-cell system with a platinum counterelectrode and a saturated calomel reference electrode (SCE). The workingelectrode was fabricated by repeated casting (twice) 10 μpL of PPy/CNC(1 mg mL-1 in 50% water/ethanol) dispersion onto graphite carbon (GC)electrode (3 mm in diameter). CV tests were performed between −0.6 and0.4 V versus SCE in KCl electrolyte (0.5 M). The Cs result from CV testsof different PPy/PVP/CNC samples were plotted and compared in FIG. 8 .The specific capacitance continued to increase from 3 hours until itapproached a peak value of between 260 to 320 F/g at 16 hours, anddecreased sharply after that. Though the conductivity approached athreshold at 3 hours, the capacitance did not. The capacitance reachedits optimal levels when CNC/PVP was evenly coated with PPy. The sharpdecrease in the capacitance was attributed to the thick and rough PPycoating, which hindered the ion diffusion and charge transfer. The bestperformance of PPy/PVP10/CNC in the CV test possessed a capacitance of323 F/g, which is better than systems prepared with graphene or CNT.

The superior Cs is likely due to the nanoporous network formed by the IDrod-shaped PPy/PVP/CNCs that possessed significant active surface areafor the efficient ion diffusion and transport. Moreover, the lightweightsubstrate material of CNC and ultrathin and uniform layer of PPy coatingalso contribute to the high Cs. Within the supercapacitor field, carbonnanotube (single walled/multiwalled) and graphene have arousedtremendous interest in the past due to their super-conductive nature.Table 2 lists the capacitance of carbon nanotube and graphene basedelectrode materials from different studies as a comparison to thisdisclosure.

TABLE 2 Capacitance measured in different studies on Single-walledcarbon nanotube (SWCT). Multi walled carbon nanotube (MWCT), PPy- coatedMWCT, graphene sheet, nanocomposite of PPy and graphene. Scan SpecificMaterial Electrolyte Rate Capacitance Ref SWCT 7.5M KOH  0.1 V/s 180 F/gAn et al. 2001 MWCT   6M KOH 0.01 V/s 135 F/g Frackowiak et al. 2000PPy/ 1M H₂SO₄ 0.01 V/s 170 F/g Frackowiak et al. 2001 MWCT Graphene1MNa₂SO₄ 0.01 V/s 135 F/g Y Li et al. 2011 PPY/ 1M KCl 0.01 V/s 223 F/gY Han et al. 2010 Graphene PPy/ 0.5M KCl 0.01 V/s 239 F/gPCT/CA2014/050570 TEMPO- 0.05 V/s 225 F/g CNC  0.1 V/s 220 F/g PPy/0.5MKCl  0.0 V/s 323 F/g This disclosure PVP10/ 0.05 V/s 284 F/g CNC 0.1 V/s 270 F/g (An et al. 2001): An, K. H.; Kim, W. S.; Park, Y. S.;Moon, J. M.; Bae, D. J.; Lim, S. C.; Lee, Y. S.; Lee, Y. H., AdvancedFunctional Materials 2001, 11(5), 387-392; (Frackowiak et al. 2000):Frackowiak, E.; Metenier, K.; Bertagna, V.; Beguin, F., Applied PhysicsLetters 2000, 77(15), 2421-2423; (Frackowiak et al, 2001): ) FrackowiakE., J. K., Delpeuk S., Beguin F., J. Power Sources 2001, 822, 97- 98. (YLi et al. 2011) Yueming Li, M. v. Z., Shirley Chiang, Ning Pana, Journalof Power Sources 2011, 196, 6003-6006. (Y Han et al. 2010): Yongqin Han,B. D. a. X. Z., Journal of New Materials for Electrochemical Systems2010, 13, 315-320.

Comparison of Capacitance Loss Between PPy/PVP10/CNC and PPy/TempoCNC

The stability during charge and discharge is a critical issue that isclosely associated with the properties/morphologies of the activematerial. Thus, the CV stability tests were performed on PPy/TempoCNC(Py/OH=16) and PPy/PVP10/CNC. Although the Py/OH ratio is defined inPCT/CA2014/050570, a short description follows.

Py/OH refers to the molar ratio of initial pyrrole monomer (Py), to thesurface hydroxyl groups (OH) on CNC. The molar amount of surfacehydroxyl group on CNC can be calculated on the basis that CNC is made-upof anhydroglucose units (AG U) that possess a molecular weight of 162g/mol, each AGU contain three hydroxyl groups however about 20% ofhydroxyl group are exposed on the surface of CNC. The following formulacan be used, (wherein X is the amount in grams of CNC used):3*(Xg/162(g/mol)*0.2=Z mols of surface hydroxyl groups. For example,when 1 gram of CNC is used the molar amount of hydroxyl group was 3*(1g/162(g/mol))=0.0185 mol*20%=0.0037 mol.

The capacitance loss over cycling was plotted in FIG. 9. The cyclingstability was greatly enhanced in the PPy/PVP/CNC system with less thana 9% capacitance loss compared to a 35% loss for the PPy/Tempo-CNCsystem. The superior cycling stability is attributed to a more uniformPPy deposition that facilitates the charge transfer and diffusion. Inaddition, the affinity between PVP and PPy driven by hydrophobicinteraction and hydrogen bonding provided a stronger and robust PPycoating. The enhanced cycling stability could also be due to thepseudo-3-layer structure of the PPy/PVP/CNC. The layer in the middleformed by PVP polymer chains serves as a buffer that effectivelyreleases stress induced by ion diffusion/electron transfer within thehybrid material. This is especially advantageous compared to the2-layered PPy/CNC model where there is no binder at the interface toprovide flexibility between the substrate and the PPy sheath.

Comparison of PPy/PVP10/CNC and PPy/Tempo-CNC (PCT/CA2014/050570)Synthesis and Processes.

Table 3 compares one embodiment of this disclosure with TEMPO-oxidizedCNCs prepared in accordance with PCT/CA2014/050570. The key advantagesof the new approach are: (i) the synthesis is conducted in mild pHcondition, instead of very low pH environment needed for TEMPO-CNC; (ii)physical adsorption of PVP onto CNC is simpler than TEMPO-mediatedoxidation of CNC for enhanced affinity between the substrate and PPy.

The ZP of PPy/PVP10/CNC was positive while PPy/TempoCNC possessed anegative ZP at −31 mV, suggesting that a more uniform and better coatingof PPy was achieved for PVP/CNC system. Secondly, the conductivity ofPPy/PVP/CNC increased by 7 times (conductivity increased from 4.9 to36.9 S/cm), which is largely attributed to the improved PPy coating.PPy/Tempo-CNC produced a globular PPy coating morphology with sporadiccoverage on the CNC nanorods, whereas PPy/PVP/CNC displayed a uniformcore-sheath structure covering most of the CNC surface. An enhancementof 35% in the specific capacitance was observed for the PPy/PVP/CNCsystem.

TABLE 3 PPy/TempoCNC PPy/PVP/CNC Synthesis pH Low Neutral Surfacemodification TEMPO-mediated PVP of CNC oxidation adsorption ZetaPotential −31 mV +16.1 mV Conductivity 4.9 S/cm 36.9 S/cm Capacitanceloss after 16.9% 8.9% 1000 cycles

While the disclosure has been described in connection with specificembodiments thereof, it is understood that it is capable of furthermodifications and that this application is intended to cover anyvariation, use, or adaptation of the disclosure following, in general,the principles of the disclosure and including such departures from thepresent disclosure that come within known, or customary practice withinthe art to which the disclosure pertains and as may be applied to theessential features hereinbefore set forth, and as follows in the scopeof the appended claims.

1. A composite having a core-shell arrangement, said compositecomprising cellulose nanocrystal (CNC) as the core, a first layercomprising at least one surface agent in contact with said CNC and asecond layer comprising at least one intrinsically conductive polymer(ICP) in contact with said surface agent.
 2. The composite of claim 1,wherein said surface agent is an amphiphilic agent.
 3. The composite ofclaim 1, wherein said surface agent is poly(4-vinylpyridine) (P4VP),poly(N,N-dimethyl acrylamide) (PDMA). poly(N,N-dimethyl acrylamide)(GTMAC), Polyethylenimine(PEI), or poly(N-vinylpyrrolidone) (PVP). 4.The composite of claim 1, wherein said ICP is polypyrrole, polyaniline,polyindole, polythiophene, poly(3-methylthiophene, poly(N-methylaniline), or poly(o-toluidine).
 5. The composite of claim 1, wherein amass ratio of the surface agent/CNC is from about 5/100 to about100/100.
 6. A process for preparing a composite having a core-shellarrangement, said composite comprising cellulose nanocrystal (CNC) asthe core, a first layer comprising at least one surface agent in contactwith said CNC and a second layer comprising at least one intrinsicallyconductive polymer (ICP) in contact with said surface agent; saidprocess comprising; dispersing the cellulose nanocrystal (CNC) in asolution; mixing the CNC solution and at least one surface agent tocause adsorption of said surface agent on the CNC surface and form saidfirst layer; adding at least one monomer of said intrinsicallyconductive polymer (ICP) and polymerizing said monomer to form saidsecond layer in contact with said first layer comprising the surfaceagent; and isolating said composite.
 7. The process of claim 6, whereinsaid surface agent is poly(4-vinylpyridine) (P4VP), poly(N,N-dimethylacrylamide) (PDMA), poly(N,N-dimethyl acrylamide) (GTMAC),Polyethylenimine(PEI), or poly(N-vinylpyrrolidone) (PVP).
 8. The processof claim 6, wherein said ICP is polypyrrole, polyaniline, polyindole,polythiophene, poly(3-methylthiophene, poly(N-methyl aniline), orpoly(o-toluidine).
 9. The process of claim 6, wherein a mass ratio ofthe surface agent/CNC can range from 5/100 to 100/100.
 10. The processof claim 6, wherein said ICP is added dropwise to the reaction mixture.11. The process of claim 6, further comprising a step of quenching aftersaid polymerization of said ICP before said step of isolating saidcomposite.
 12. The process of claim 11, wherein said step of isolatingof said composite is comprising removing excess oligomers and unreactedchemicals.
 13. The process of claim 6, further comprising a step ofprocessing after said step of isolating said composite.
 14. The processof claim 13, wherein said step of processing is comprising drying,pressing or casting.
 15. A process for preparing a supercapacitorelectrode comprising casting a slurry of the composite having acore-shell arrangement as defined in claim 1 on an electrode followed bydrying of said slurry.